Crystal Follies

In his book Kaleidoscope Sky, naturalist Tim Herd explains the gamut of wonders that one can see in our atmosphere, some of which are shown in this gallery.

An Austrian ski resort provided this image of ice crystals. The crystals act like prisms, bending the sunlight at no less than 22 degrees. Thus, that ring you see is called a 22-degree halo, and its inside appears dark because light is bent away from it.

When Boats Fly

Don't believe the cartoons--mirages don't happen solely in the desert. Light bends anytime it passes through air, but when the air temperature varies dramatically over a short distance, causing it to have great fluctuations in density, it can bend light so much that a mirage occurs.

This image is called a superior mirage because it makes the boat look taller than it actually is. And superior mirages always include a portion of the picture that's inverted, as you can see here.

Two Sunsets in One Day

The refraction of sunlight usually makes the sun appear flatter or more oval on the horizon during sunsets. This sunset over the Pacific Ocean, photographed by the European Southern Observatory in Chile, is a more pronounced version of that visual effect.

Refraction severely flattens the top of the sun, but its light is brighter because of a shorter trip through the atmosphere. The double sun seen below is called an inferior mirage. This is the most common type of mirage, the one we see all the time on highways on hot days.

Aurora in Red

Subatomic particles fly out from the sun constantly, in what we call the solar wind. Luckily for living beings, the Earth's magnetosphere deflects most of these particles away from us.

But at the planet's far polar regions, some of these particles enter our atmosphere and provide the sweeping light shows we know as auroras.

Auroras emit light in colors across the visible spectrum, but just a few dominate, with green being the most common color. Ionizing oxygen high in the Alaska skies allowed for these rare red aurora rays.

Look What I Caught in My Web

Rainbows can form when light shines through water droplets in the air--the standard rainbow that we see not infrequently.

But if the sun shines in at a low angle, they can also appear when water droplets affix to certain surfaces, like the dew on this spiderweb. Grass, heather, and other small plants are also good surfaces for dewbows.

Taking the "Bow" out of "Rainbow"

This flat rainbow is called a circumhorizontal arc, a rare phenomenon that can form only when the sun is above 58 degrees in the sky and shines through plates of ice crystals. This one showed up in Spokane, Washington, in 2006.